This invention relates to polyurethane adhesives, and to substrates coated with a layer of a polyurethane adhesive.
Polyurethane adhesives and sealants of various types are well known. See, e.g., U.S. Pat. Nos. 3,779,794, 4,624,996 and 4,625,012.
In certain applications, it is desirable to provide an adhesive which, once applied to a substrate and cured, can be removably attached to an underlying surface. For these applications, a combination of tenacious bonding and yet virtual absence of residual adhesive on the underlying surface upon removal is desired. Upon removal, the exposed adhesive often picks up dirt and dust. It is further desirable that the adhesive is such that it can be washed without destroying its tackiness.
An example of such an application is carpet, especially carpet tiles or automotive floor mats, which must be adhered to the floor or other substrate. This is often done by applying a pressure sensitive adhesive to the floor, and applying the carpet to the adhesive. Although the carpet is easily removed when applied in this manner, the adhesive stays with the floor when the carpet is removed. Moreover, the adhesive often bonds too strongly to the carpet, and weaker carpet backings such as polymeric foams often tear and leave portions of the backing attached to the floor. This increases the difficulty of completely removing the carpet.
It would be desirable to provide a polyurethane adhesive which adheres tenaciously to a substrate, yet is cleanly removable and washable.